Method of and apparatus for handling articles



Oct. 25, 1966 B. SASSEN ETAL 3,280,959

METHOD OF AND APPARATUS FOR HANDLING ARTICLES Original Filed April 27, 1962 s sheets-sheet 1 F'IB I- INVENTORS BERNARD SASSEN PHILIP NISENBAUM HAROLD J. YOUNG BY WW ATTORNEY Oct. 25, 1966 B. SASSEN ETAL 3,280,959 METHOD OF AND APPARATUS FOR HANDLING ARTICLES Original Filed April 27, 1962 5 Sheets-Sheet 2 mvsu'rons BERNARD SASSEN PHILIP NISENBAUM m HAROLD .1. YOUNG 5 BYZMWW ATTORNEY Oct. 25, 1966 B. SASSEN ETAL METHOD OF AND APPARATUS FOR HANDLING ARTICLES Original Filed April 27. 1962 mquullll l i 5 Sheets-Sheet 5 INVENTORS BERNARD SASSEN PHILIP NISENBAUM HAROLD J- YOUNG ATTORNEY United States Patent Office 3,280,959 Patented Oct. 25, 1966 3 280,959 METHOD OF AND AFPARATUS FOR HANDLING ARTICLES Bernard Sassen, Los Gatos, and Philip Nisenbaum and Harold J. Young, San Jose, Calif., assignors to FMC Corporation, San Jose, Calif., a corporation of Delaware Original application Apr. 27, 1962, Ser. No. 190,550, now Patent No. 3,219,204, dated Nov. 23, 1965. Divided and this application Jan. 25, 1965, Ser. No. 433,833

5 Claims. (Cl. 19821) This invention relates to apparatus for feeding a stack of thin articles such as letters to a pick-off device which removes the letters one by one from the forward end of the stack.

This application is a division of Serial No. 190,550, filed April 27, 1962, now Patent No. 3,219,204, issued November 23, 1965, and assigned to the assignee of the present invent-ion.

'In article handling systems of the type requiring the picking-off or singulation of individual flat, thin articles (such as letter mail) from a stack of these articles, two conflicting conditions must be met. To explain this, reference will be made to the handling of a stack of letters in a Post Ofiice installation.

First, the stack of letters must be kept in their upright condition (on edge). This requires that as the stack is depleted by the singulator, a back-up plate or the like must be progressively advanced to maintain the stack upright.

Second, excessive friction between the leading letter, namely, the letter being withdrawn from the stack, and

V the stack feeder of the the next adjacent letter, cannot be tolerated. Excessive friction here would cause at least the next adjacent letter to slide out from the stack along with the leading letter, which is to be withdrawn singly.

These conflicting conditions are reconciled by the stack feeding system of the present invention. The stack of letters is on a tray and the tray is advanced against a spring stop by a reversible rotary drive mechanism. The tray can be both advanced and withdrawn (retracted) by the drive mechanism, and since the latter is rotary, speed reducer mechanism can be used to increase the sensitivity of the control. The drive mechanism is controlled by the spring stop itself, which is incorporated in the control. The spring stop and control are set so that at the neutral position, the drive mechanism, and the letter tray are stationary, but in this position the s ring exerts a prescribed force on the stack of letters. This force is adequate to support the stack, but inadequate to cause difficulties due to friction follow-up by the litters behind that being Withdrawn from the stack.

This feeding mechanism and control are such that the aforesaid preselected force will be automatically restored immediately after letters are withdrawn from the stack. Withdrawal of each letter causes the spring loaded stop to move by the letter thickness under the spring force.

Since the stop is incorporated with the drive control in a manner which varies with the displacement of the stop from its neutral position, withdrawal of a letter from the stack starts up the drive mechanism and advances the letter tray until the preselected spring force is re-established. Being both reversible and displacement responsive, the drive rapidly restores the system to neutral, at the pre-selected spring force.

bjects of the present invention are:

To maintain a preselected spring force on a stack of thin articles such as letters in a stack feeder.

To attain the above for various letter thicknesses, i.e., to advance the feeder in increments that correspond to the thickness of individual letters of varying thickness, as they are withdrawn from the stack.

To provide an automatic feed of the type described which is automatically variable in speed in either direction.

To provide such an apparatus which will rapidly restore the preselected spring force after letter withdrawal. This advantage of rapid action results from the type of drive described. Being reversible, it can momentarily overshoot and return, hence reaching the neutral position more rapidly than if it crept up to the neutral position.

In the above, it is to he understood that reference to a stack of letters is merely exemplary. Other thin, fiat articles such as cards, checks, etc., can be handled by the mechanism of this invention.

The manner in which these advantages and objects may be attained will be apparent from the following description of the invention, taken with the accompanying drawings.

In the drawings:

FIG. 1 is a fragmentary diagrammatic perspective of a reading, coding and presorting apparatus embodying present invention.

FIG. 2 is an enlarged, fragmentary, diagrammatic perspective showing the left end of the system of FIG. 1 "in greater detail.

FIG. 3 is an enlarged fragmentary diagrammatic perspective looking in the direction of arrow 3 of FIG. 2 showing a portion of a tray feed conveyor and the letter singulator, certain parts being broken away and parts of the drive mechanism removed.

FIG. 4 is a schematic section showing the path of movement of the vacuum operated letter pick-up head shown in FIG. 3.

FIG. 5 is a schematic diagram of the hydraulic control circuit of the tray feed conveyor drive unit of this invention.

As mentioned, the stack feeder of the present invention will be described embodied in a Post Ofiice letter sorting system which includes a reading, coding, and presorting apparatus 20 (FIG. 1) having a plurality of coding stations A. Trays T having stacks of letters L are fed into each coding station A by a tray conveyor 36 and an incremental drive system 37 of the present invention. The letters are withdrawn from their stacks and automatically placed one at a time on an inclined easel 22 by singulators 38.

An operator at each station A reads the address on the letters L .as they are moved along the easel 22 by a letter transporting conveyor 23. The operator controls a keyboard 24 that causes a coded marking to be imprinted on each letter by a printing unit 26 (for use in another portion of the system, not shown but explained in detail in the aforesaid parent application), and also causes a pre-sort signal to be placed into a memory unit (also not shown). When the conveyor 23 brings the letter to its destination, the pre-sort signal causes each letter to subsequently be placed into one of a plurality of letter transfer and stacking mechanisms 27. In the system shown, each conveyor 23 is indexed by the operator associated with that station, to advance each letter along the easel 22 until it reaches the selected mechanism 27. The details of the stacker mechanism 27 form no part of the present invention, this mechanism forming the subject matter of our copending divisional application Serial No. 433,834, filed January 25, 196-5, and assigned to the assignee of the present invention.

The stack feeder of the present invention, including the tray conveyor 36 which supplies letters to the singulators 38 at the coding stations A, is best seen in FIG. 2. The external mechanical construction of the feeder control 37 and the letter pickotf head for singulator 38 are shown in FIG. 3. The relation of the tray conveyor portion of the feeder of this invention to the FIG. 4. The hydraulic feeder control is shown in FIG. 5. These elements will now be described in detail, except for the singulator 38, the details of which are not critical to the invention.

At each coding station A the tray conveyor 36 is operated by a control in the form of an incremental drive mechanism 37, which advances the tray T in increments equal to the thickness of the letters being removed therefrom by a singulator 38. The singulator has a drive 39 (FIG. 3), and it is paced by the operator, as described in the aforesaid Patent 3,219,204. The singulator 38 has a pick-up head 40 which follows a path P (FIG. '4) for withdrawing the leading letter from the stack and placing it on the associated easel 22.

Each tray T comprises an open-ended generally U- shaped body 41 having a plurality of vertical grooves 42 in each vertical side wall 43. Two removable end plates 44 are each placed in aligned grooves 42 in the walls 43 and are spaced apart a distance sufficient to support the letters thereon in substantially vertical planes parallel to the end plates 44. The letters, which may be of any standard size, are cancelled and placed upright in the trays T with the addresses facing the operator so that they can be read by the operator.

The tray conveyor 36 (FIG. 2) comprises an endless steel band 46 having a plurality of evenly spaced upstanding lugs 47 thereon. The band 46 is trained around end rolls 48 and 49 which are journalled in parallel spaced side plates 51 and 52 of the frame 53 of the associated station. The trays T are supported by a plurality of rollers 54 projecting inwardly from the opposed side plates 51 and 52. Each filled tray T is placed on the rollers 54 by an operator with at .least one of the. lugs 47 fitted in a slot (FIG. 4) formed between a pair of depending lugs 55 on the underside of the tray T so that the tray can be moved toward or away from the operator in response to similar movement of the steel band 46. The upper run of the steel band 46 is normally driven in the direction of the arrow C (FIG. 2) by the incremental drive mechanism 37 which includes a chain drive 56 connected to the roller 49.

The incremental drive mechanism 37 for each tray conveyor 36 includes a sensing finger 61 (FIG. 3) which extends through a slot 62 in the end plate 44 of the tray being emptied and abuts the foremost letter therein. The sensing finger 61 is pivotally supported by identical parallel bars 63 and 64 which are pivoted to a housing 66 of a servo valve 67 by pins 68 and 69, respectively.

The servo valve 67 is connected in a closed hydraulic circuit 71 (FIG. which includes a continuously dn'ven pump 72 that forces hydraulic fluid through a conduit 73 to a diiferential flow divider 74 having a flow controlling spool 76 therein. A return line 75 leads to the pump 72. When the valve core 77 of the servo valve 67 is in the central position shown in FIG. 5, equal amounts of fluid flow past the ends of the spool 76 and out of both ends of the flow divider 74 through conduits 78 and 79 respectively. The flow of hydraulic fluid continues past a reduced diameter portion 81 of the valve-core 77 and returns to the pump 72 through a conduit 82 and return line 75. A hydraulic drive motor 83 is connected in parallel with the flow divider 74 and between the conduits 78 and 79 by branch conduits 84 and 86, respectively. It will be recognized that as long as the valve core 77 remains centered in the position shown in FIG. 5, fluid will not flow through the motor 83 and accordingly its drive shaft87 will not rotate. The drive shaft 87 is connected by a chain drive 88 to the input shaft 89 of a gear reducer 91. The output shaft 92 of the gear reducer 91 is connected by the aforementioned chain drive 56 to the roller 49 (FIG. 2) of the associated tray conveyor 36.

A compression spring 96 urges the valve core 77 out-. iwardly against the bar 63 which carries the sensing finger letter easel appears in p direction indicated by the arrows.

61. The spring 96 is very weak and can be overcome sufficiently to move the valve core 77 past its vertical position by a force of approximately two to four ounces acting on the finger 61. When a letter is not being contacted by the finger 61, the spring 96 will urge the valve'core 77 downwardly as viewed in FIG. 5 until the flow through the conduit 78 is blocked by a portion 77a of the core 77 and the conduit 79 is completely opened. The pressure in conduit 79 is thus lower than the pressure in conduit 78 and, accordingly, the spool 76 of the flow-divider 74 is moved downwardly (FIG. 5) causing a major portion of the hydraulic fluid to be diverted into the conduit 78. Thus, fluid flows through the branch conduit 84, through the motor 87, through the branch conduit 86, through a portion of the conduit 79, through the servo valve 67, and returns to the pump 72 through the conduit 75. The hydraulic motor 83 is thus driven at its maximum speed which advances the conveyor 36 and tray T of letters thereon toward the operator at the rate of approximately two feet per second. It is to be understood that the spool 76 of the flow divider 74 may be placed in intermediate positions and that the position of the spool 76 cooperates with the flow divider to not only determine the direction of flow but to also determine the rate of flow in either direction according to the pressure exerted on the sensing finger 61 by the letters.

When the tray is moving toward the operator and the first letter contacts the sensing finger 61, the valve core 77 is abruptly moved inwardly against the urging of the spring 96 causing a core portion 77b to close the conduit 79 and open the conduit 78 thus causing the motor 83 and conveyor 37 to be momentarily driven in a reverse direction. The conveyor will thereafter be moved forward and reverse in a flutter type action in minute increments until the foremost letter exerts a tWo to four ounce force against the sensing finger 61 which balances the force of the spring 96 and causes the valve core 77 to assume the central position shown in FIGURE 5. It is to be understood that the elapsed time from the moment of contact of the sensing finger 61 to the, moment when the tray is at rest is too rapid to be perceptible and the oscillation of the tray cannot be visibly detect-ed.

After the foremost letter has been removed from the tray T and placed on the associated easel 22, the tray moves forward one letter thickness until a two to four ounce force is again applied to the sensing finger 61. This procedure is repeated for each letter, in turn.

As mentioned, the singulator 38 has a head 40 which picks up one letter at a time from the letter tray T, and places the letters on the easel 22. The singulator is cycled by the operator after reading the address on a previously singulated letter. The drive mechanism for the singulator head is shown in FIG. 3 and will be described briefly, these details not forming part of this invention, reference being made to the aforesaid Patent 3,219,204 for a complete description.

The singulator vacuum pickup head 40 is mounted on the lower end of a vertical pickup arm 102, and the pickup head 40 is moved along the path P (FIG. 4) in the The pickup arm 102 is reciprocated both horizontally and vertically along the path P by barrel cams 107, 108 and 109 in the housing 106. The singulator is driven by the belt 39 and is caused to move through a letter delivery cycle under control of the operator, by a system described in detail in the aforesaid patent. V

As mentioned previously, the foremost letter is gripped by the vacuum head 40, removed from the tray, and carried to a position closely adjacent the easel 22 as indicated in FIGURE 4. When the letter is within a quarter inch from reaching the easel 22, the vacuum is released and air pressure of about three or four p.s.i. blows the letter off the pickup head onto the associated easel 22.

The singulation operation is rapid and is accomplished without withdrawing more than one letter at a time from the stack because of the precise, yet rapid operation of the stack feeder mechanism 36, 37 of the present invention.

While one embodiment of the present invention has been shown and described, it will be understood that various changes and modifications may be made without departing from the spirit of the invention or the scope of the appended claims.

Having thus described the present invention and the manner in which the same is to be used, what is claimed as new and is desired to be protected by Letters Patent is:

1. Apparatus for advancing a stack of thin articles, such as letters, to a pickoff head which slides the leading article clear of the stack in a transverse direction, said apparatus comprising an article conveyor, means on said conveyor for advancing the stack, means for driving said conveyor comprising a reversible rotary motor and a speed reducer connected to the conveyor, control means for causing said conveyor driving means to run in either direction and at a speed proportional to the displacement of the control means from a neutral position, an article sensor for engaging the leading article in the stack and connected to operate said control means, and spring means for biasing said sensor into engagement with the leading article and simultaneously biasing said control means to one side of a neutral position in a direction for advancing the conveyor, said control means assuming its neutral position with the conveyor stationary and with said spring means exerting a preselected force on the stack, said control means assuming a position on the other side of its neutral position for causing said driving means to retract the conveyor when said conveyor has advanced sufficiently to cause said spring means to exert more than said preselected force on the stack.

2. Apparatus for automatically advancing a stack of thin articles, such as letters, comprising an article conveyor, means on said conveyor for advancing articles, a hydraulic pump, liquid flow control means, a pair of parallel conduits for receiving liquid from said pump and directing it to said flow control means, a liquid discharge line leading from said flow control means, a reversible rotary hydraulic motor connected across said conduits, said flow control means comprising valve means for selectively varying the relative flow of liquid in said conduits with a corresponding change in the direction and speed of rotation of said hydraulic motor, means biasing said valve means in one direction for moving said valve means from a hydraulic motor reverse drive position, past a vertical position where said motor is stationary, and on to a forward drive position, and article sensing means for moving said valve means in the other direction in response to a force applied to said sensing means by the articles on said conveyor.

3. The apparatus of claim 2, wherein said flow control means comprises a balanced inlet pressure, flow responsive dual check valve having its inlet connected to said pump and its outlets connected to the inlets of said conduits upstream of said motor.

4. The apparatus of claim 2, wherein said valve biasing means includes a spring, which maintains a preselected force loading on the articles when said valve means is in its neutral position with the motor stationary.

5. In an apparatus for handling data bearing articles such as letters, the combination of an endless tray conveyor, a plurality of spaced lugs on said conveyor, a tray adapted to hold a plurality of upstanding letters and having an opening in its lower surface receiving one of said lugs, a hydraulic motor connected to said conveyor for driving said conveyor in either direction, a closed hydraulic circuit connected to said hydraulic motor, a pump in said circuit for directing hydraulic fluid through said circuit, a flow divider in said circuit for receiving fluid from said pump and for dividing and discharging the fluid into two streams, a pair of branch conduits connected to said flow divider and to a flow control valve for receiving said two streams and for directing said streams into said valve, said hydraulic motor being connected in parallel between said conduits, flow control means in said valve operative to selectively increase the restriction to flow of fluid in one of said conduits while decreasing the restriction to flow in the other of said conduits whereby fluid pressure in one of said conduits is greater than the pressure in the other of said conduits causing the fluid to pass through said hydraulic motor and drive said motor in one direction, resilient means normally urging said flow control means to a position to cause said hydraulic motor to drive said conveyor and said letter-filled tray in a forward direction, and letter sensing means operatively connected to said flow control means and operable in opposition to said resilient means to move said control means into a neutral position stopping said motor when the foremost letter in the tray is bearing against said sensing means with a force equal to that of said resilient means.

References Cited by the Examiner UNITED STATES PATENTS 2,530,670 11/1950 Von Hofe 27131 3,051,297 8/1962 Helm et al 198203 X EVON C. BLUNK, Primary Examiner.

SAMUEL F. COLEMAN, Examiner.

R. I. HICKEY, Assistant Examiner. 

1. APPARATUS FOR ADVANCING A STACK OF THIN ARTICLES, SUCH AS LETTERS, TO A PICKOFF HEAD WHICH SLIDES THE LEADING ARTICLE CLEAR OF THE STACI IN A TRANSVERSE DIRECTION, SAID APPARATUS COMPRISING AN ARTICLE CONVEYOR, MEANS ON SAID CONVEYOR FOR ADVANCING THE STACK, MEANS FOR DRIVING SAID CONVEYOR COMPRISING A REVERSIBLE ROTARY MOTOR AND A SPEED REDUCER CONNECTED TO THE CONVEYOR, CONTROL MEANS FOR CAUSING SAID CONVEYOR DRIVING MEANS TO RUN IN EITHER DIRECTION AND AT A SPEED PROPORTIONAL TO THE DISPLACEMENT OF THE CONTROL MEANS FROM A NEUTRAL POSITION, AN ARTICLE SENSOR FOR ENGAGING THE LEADING ARTICLE IN THE STACK AND CONNECTED TO OPERATE SAID CONTROL MEANS, AND SPRING MEANS FOR BIASING SAID SENSOR INTO ENGAGEMENT WITH THE LEADING ARTICLE AND SIMULTANEOUSLY BIASING SAID CONTROL MEANS TO ONE SIDE OF A NEUTRAL POSITION IN A DIRECTION FOR ADVANCING THE CONVEYOR, SAID CONTROL MEANS ASSUMING ITS NEUTRAL POSITION WITH THE CONVEYOR STATIONARY AND WITH SAID SPRING MEANS EXERTING A PRESELECTED FORCE ON THE STACK, SAID CONTROL MEANS ASSUMING A POSITION ON THE OTHER SIDE OF ITS NEUTRAL POSITION FOR CAUSING SAID DRIVING MEANS TO RETRACT THE CONVEYOR WHEN SAID CONVEYOR HAS ADVANCED SUFFICIENTLY TO CAUSE SAID SPRING MEANS TO EXERT MORE THAN SAID PRESELECTED FORCE ON THE STACK. 